Few things more annoying to a driver than smelling a putrid smoke cloud coming from the tailpipe of an old beatup car that you just know is spewing all kinds of foul emissions into the air.

Thankfully, each year there are fewer and fewer of these smog makers still on the road, now so few that the Environmental Protection Agency is considering dropping or phasing out tailpipe emissions tests for these dinosaurs. Independent testers also say there are too few cars over 18-years-old still on the road for the bulk of testing stations to justify spending thousands of dollars on specialized emissions testing equipment. They’re both right and the region could benefit from smarter emissions regulation over an outdated one-size fits all approach.

Cars of any age are the biggest spewers of nitrogen oxides, a precursor to lung-choking bad air that can cause bronchitis, emphysema and aggravate heart conditions. Gradually ending testing of cars that already are 18-years-old or older would allows resources and investments to be deployed where they can do the most good -- making sure that newer, cleaner cars stay clean. At the same time, the shift would free the vast majority of testing stations from having two types of expensive equipment to conduct emissions tests.

Currently, cars from model years 1990-95 are put on rollers to simulate driving conditions as part of a test of tailpipe emissions, and newer cars, which are several times cleaner, are tested through a cheaper, sophisticated diagnostic technology built into the vehicle. The equipment to test older cars costs about $40,000 and requires a $4,000 yearly service contract, considerably more than the equipment needed to test newer models. To no one’s surprise, older cars flunk emissions tests more often than newer models, but there has be a middle ground that balances the cost of testing a diminishing number of older cars against making sure newer cars remain road worthy.

But rather than require independent testers to invest in expensive little-used equipment that impacts about 6 percent of cars, a wiser alternative would be to allow older cars to be tested at a few convenient centralized stations subsidized and licensed only to operate the older equipment. Older cars would still get an examination and other testing stations could concentrate on the newer cars. The transition would be gradual, say over five years, so testers could make the adjustment and smoke-belchers wouldn’t foul North Texas air with impunity.

Although Texas’ testing program, financial incentives to repair or replace older vehicles and crackdowns on vehicles emitting visible exhaust emissions have improved air quality, ozone levels in North Texas are higher than the EPA’s national health standard. Now is not the time to for the region to turn its back on progress, by it is time to consider better ways to maintain it.

Key facts about auto emissions testing in North Texas

11 percent of pre-1996 cars tested in 2012 flunked.

4 percent of newer cars failed in 2012.

6 percent of cars on road predate 1995.

1.5 times more pollution is produced when an older model car fails.

SOURCE: North Central Texas Council of Governments, Texas Commission on Environmental Quality, Texas Department of Public Safety, Environmental Protection Agency